Math Problem Statement

Find dy/dx by implicit differentiation. tan^(−1)(3x^2y) = x + 5xy^2

Solution

To find dydx\frac{dy}{dx} by implicit differentiation for the equation:

tan1(3x2y)=x+5xy2\tan^{-1}(3x^2y) = x + 5xy^2

we will differentiate both sides of the equation with respect to xx.

Step 1: Differentiate the left-hand side

The left-hand side is tan1(3x2y)\tan^{-1}(3x^2y). We'll use the chain rule to differentiate it:

ddx[tan1(3x2y)]=11+(3x2y)2ddx(3x2y)\frac{d}{dx}\left[\tan^{-1}(3x^2y)\right] = \frac{1}{1 + (3x^2y)^2} \cdot \frac{d}{dx}(3x^2y)

Next, differentiate 3x2y3x^2y:

ddx(3x2y)=3(2xy+x2dydx)=6xy+3x2dydx\frac{d}{dx}(3x^2y) = 3 \cdot (2x \cdot y + x^2 \cdot \frac{dy}{dx}) = 6xy + 3x^2 \frac{dy}{dx}

So the derivative of the left-hand side becomes:

11+(3x2y)2(6xy+3x2dydx)\frac{1}{1 + (3x^2y)^2} \cdot (6xy + 3x^2 \frac{dy}{dx})

Step 2: Differentiate the right-hand side

The right-hand side is x+5xy2x + 5xy^2. Differentiating term by term:

  1. ddx(x)=1\frac{d}{dx}(x) = 1
  2. ddx(5xy2)=5(y2+2xydydx)=5y2+10xydydx\frac{d}{dx}(5xy^2) = 5 \cdot (y^2 + 2xy \cdot \frac{dy}{dx}) = 5y^2 + 10xy \frac{dy}{dx}

So, the derivative of the right-hand side is:

1+5y2+10xydydx1 + 5y^2 + 10xy \frac{dy}{dx}

Step 3: Set the derivatives equal

We now have:

11+(3x2y)2(6xy+3x2dydx)=1+5y2+10xydydx\frac{1}{1 + (3x^2y)^2} \cdot (6xy + 3x^2 \frac{dy}{dx}) = 1 + 5y^2 + 10xy \frac{dy}{dx}

Step 4: Solve for dydx\frac{dy}{dx}

Distribute the left-hand side:

6xy+3x2dydx1+(3x2y)2=1+5y2+10xydydx\frac{6xy + 3x^2 \frac{dy}{dx}}{1 + (3x^2y)^2} = 1 + 5y^2 + 10xy \frac{dy}{dx}

Multiply both sides by 1+(3x2y)21 + (3x^2y)^2 to eliminate the denominator:

6xy+3x2dydx=(1+5y2)(1+(3x2y)2)+10xydydx(1+(3x2y)2)6xy + 3x^2 \frac{dy}{dx} = (1 + 5y^2)(1 + (3x^2y)^2) + 10xy \frac{dy}{dx} (1 + (3x^2y)^2)

Rearrange the equation to isolate dydx\frac{dy}{dx}:

3x2dydx10xydydx(1+(3x2y)2)=(1+5y2)(1+(3x2y)2)6xy3x^2 \frac{dy}{dx} - 10xy \frac{dy}{dx} (1 + (3x^2y)^2) = (1 + 5y^2)(1 + (3x^2y)^2) - 6xy

dydx[3x210xy(1+(3x2y)2)]=(1+5y2)(1+(3x2y)2)6xy\frac{dy}{dx} \left[3x^2 - 10xy (1 + (3x^2y)^2)\right] = (1 + 5y^2)(1 + (3x^2y)^2) - 6xy

dydx=(1+5y2)(1+(3x2y)2)6xy3x210xy(1+(3x2y)2)\frac{dy}{dx} = \frac{(1 + 5y^2)(1 + (3x^2y)^2) - 6xy}{3x^2 - 10xy (1 + (3x^2y)^2)}

This is the expression for dydx\frac{dy}{dx}.

Would you like further details or explanations on any part of this process?

Related Questions:

  1. How do you apply implicit differentiation to trigonometric functions?
  2. What is the chain rule and how does it work in differentiation?
  3. How do you simplify expressions involving derivatives after applying implicit differentiation?
  4. Can you use implicit differentiation for higher-order derivatives?
  5. How does the inverse trigonometric function differentiation formula work?

Tip:

When differentiating implicitly, always remember to treat yy as a function of xx and apply the chain rule accordingly when yy appears in terms multiplied by xx.

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Math Problem Analysis

Mathematical Concepts

Implicit Differentiation
Inverse Trigonometric Functions
Chain Rule

Formulas

d/dx[tan^(-1)(u)] = 1 / (1 + u^2) * du/dx
Chain Rule: d/dx[f(g(x))] = f'(g(x)) * g'(x)

Theorems

Chain Rule for Differentiation
Derivative of Inverse Trigonometric Functions

Suitable Grade Level

Undergraduate Calculus